What about the servers you deploy to? What about the toolchain used by the upstream platform developers you depend on? What about the software powering their CI-systems?
Whatever free software they depend on, you indirectly depend on too.
Not everyone works on web applications, and I don't claim to have any knowledge of the platform that they develop with.
My point wasn't that I don't depend on free software (I absolutely do, and I do donate to the software I use every year), but that it is possible to be a developer and have very little interaction with free software.
Whatever free software they depend on, you indirectly depend on too.